This invention relates to a method and apparatus for removing the surface layer from a concrete object.
The surfaces of concrete structures such as the floors and walls of buildings housing nuclear reactors or fuel processing facilities are oftentimes subject to radioactive contamination. This contamination may be caused by neutron bombardment of the structure from radioactive sources or by spilling a solution containing radioactive material onto the surface. The radioactivity may penetrate a short distance below the surface either due to penetration of the surface by the radioactive particles or due to the natural porosity of concrete to liquids. Since, if this radioactivity is great enough, it may make the area dangerous for continued human occupation, it is imperative that the radioactivity be removed from the concrete or that the area be closed to future human occupation. Presently available methods for removing radioactive contamination from the surface layer of concrete are expensive, ineffective and possibly hazardous.
For example, the contaminated area may be removed by grinding off the surface layer. However, this method is very slow and hence expensive, and it raises a considerable amount of dust and may contribute to the spread of the contamination if the radioactive dust should become airborne. The use of this method is therefore limited to small areas of contamination because of the effort involved. The use of a torch to heat and spall small areas has also been used, but this may volatilize some radioactive isotopes, causing further contamination. The use of an acid to etch the concrete surface is still another method for removing contaminated layers. However, this may drive the radioactivity deeper into the concrete, making decontamination still more difficult. The simplest method is to seal off the contaminated area for a period of time sufficient for the radioactivity to decay to tolerable levels. However, this could involve the loss of expensive and valuable facilities for tens or even hundreds of years.